Downdraft carburetor



y 1937- G. M. HOLLEY DOWNDRAFT CARBURETOR F iled Sept. 15, 1934 5 Sheets-Sheet l QINVENTOR. 650/? N //o 4 r K I S I??? e m hr ATTURN FIY.

y 1937- G. M. HOLLEY DOWNDRAFT CARBURETOR Filed Sept. 15, 19:54 5 sheets-sheet 2 v @KI/ Ma? I, M w

INVENTOR. GHMG'! M. flour ATTORNEY.

May 18, 1937. G. M. HOLLEY.

DOWNDRAFT CARBURETOR 5 Sheets-Sheet 3 Filed Sept. 15, 1954 INVENT OR. 6:01? I2 #04; n.

ATTORNEY.

G. M. HOLLEY DOWNDRAFT CARBURETOR Filed Sept; 15, 1934- 5 Sheets-Sheet 4 6 4 2 Vacuum 14 INCHES a; M53000 runs :11 bficuwr Glass //at My INVENTOR rye M Geo RNEY May 18, 1937. G. M. HOLLEY DOWNDRAFT CARBURETOR Filed Sept. 15, 1934 5 Sheets-Sheet 5 IN\ ENTOR. Gi o/m f2 #01 z n.

W ATTORNEY.

Patented May 18, 1937 UNITED STATES 2,080,589 DOWNDBAFT CABBUBETOR George M. Holley, to Geo. M. and troit, Mlchz, a trust This invention relates to plain tube gasoline carburetors as distinguished from variable venturi and air valve carburetors. as used with automobile engines in which the maximum perform-- a'nce is required with the minimum fuel consump-' tion. Generally speaking, 'all such carburetors now provide a road load mixture ratio about leaner than the wide open throttle ratio and temporarily provide an extra fuel supply driving acceleration. Otherwise the mixture ratio is remarkably uniform.

One of the problems with these plain tube carbm'etors is to bridge the inevitable gap from the throttle running when a small idling "carburetor discharges fuel into the mixture outlet adjacent to and in advance of the throttle and when the throttle is wide open and a rich mixture is discharged into the Venturi throat of the mixture chamber. i

The nozzle construction commonly used is one in which a master regulating nozzle controls the low and high speed fuel supply and a fuel pump discharges fuel through a separate nozzle to bridge the gap when the fuel ceases to discharge from the low speed fuel nozzle and is not yet discharging from the main fuel nozzle.

Another big problem is to obtain distribution with a downdraft carburetor. carburetors were in use (3% years ago) there was quite a distance from the carburetor flange to the point in the manifold where the mixture divides and the mixture had a straight flow for this distance. Now, with the downdraft carburetor there is no room for such a distance, as when the air cleaner is installed then the carburetor and inlet manifold are designed as close together as possible and with the usual butterfly throttle the mixture is not distributed uniformly between the various cylinders. This is especially true if the throttle shaft is not located parallel to the axis of the crankshaft and a location at right angles to the axis of the crankshaft is the most convenient location for the throttle controls.

The object of this invention is, therefore, to solve these problems with a plain tube carburetor of compact form (having the greatest capacity for a given size). Specifically, my solution is to locate a butterfly throttle in the throat of the venturi of the mixing chamber into which the low speed nozzle also discharges so that the low speed nozzle supplies the major portion of the fuel so that the transitions from low and high speed may be made smoothly without the mixture ratio unduly.

the carburetor.

When updraft planes 11 and disturbin Grosse Pointe, Mich assignor Earl Holley Engines ring, De-

' Application September 15, 1934, Serial No. v4.4.1 1': Claims. (01. 261-41) The solution is complicated including a power let; an accelerating pump; and priming means, without appreciably increasing the dimension of the carburetor.

The distance from the butterfly throttleto the mixture outlet gives the best. possible distribution by the necessity e1 in the dimensions. available. With the orthodox construction the throttle-being located in the mixture outlet, this distance is not available for enabling the air stream to straighten itself out and for the mixture to distribute itself uniformly in the air stream. 1 have also discovered that by locating the throttle in the that I can get excellent performance with an unusually large throat diameter.

By arranging a small venturi to discharge against the upstream tain the effect of a variable venturi.

Fig. 1 shows a plan view of the carburetor.

Fig. 2 shows a plan view of the lower half of Fig. 3 shows a cross sectional elevation on plane H of Fig. 1 distorted so as to show the starting means in one plane.

Fig. 4 shows a cross sectional elevation on plane l -l of Fig. 1 illustrating the. accelerating means.

Fig. 5 shows a plane 5-5 of Fig. nozzle.

Fig. 6 shows cross sectional elevation on 1 illustrating the low speed a cross sectional elevation on.

Venturi throat face of this throttle, I obplane 86 of Fig. 1 illustrating the highspeed.

fuel supply means. 1

Fig. .7 shows a cross sectional elevation on plane of Fig. 1 illustrating the fuel economizing Fig. 8 shows a cross sectional elevation on plane 8-8 of Fig. 1 similar to Fig. I

Fig. 9 shows a cross sectional elevation on H of Fig. 1 similar to Fig. '7. Fig. 10 shows a fragmentary cross sectional elevation taken on ing the accelerating means.

Fig. 11 shows v v I elevation taken on plane ll.-ll of Fig. 3 showing the low speed air control- Fig. 12 shows adiagrammatic illustration of -the principle of operation without the accelerating or economy means.

Fig. 13 shows "diagrammatically the increase in Venturi depressionobtainable by the novel construction.

plane Ill-lilo! Fig. 2 showa fragmentary as. sectional Fig. 14 illustrates the method of measuring the depression in the throat of. the venturi of the novel construction.

- vented nozzle "is a well known ratio and also permits slight with the exception of the constitutes a separate in,-

. Description In Fig. 12, it is the 811 entrane'leading to a enturl tllbe inthe throat ll of which a butteris located mounted on a throttle priming means which vention.

shaft l3. Discharging into the Venturi throat II on the atmospheric side of I! is a smaller ventllri Ill. Into the throat of. a nozzle I8 discharges and is fed from two sources follows:

(a) An air vented well-l8 into which the restricted fuel outlet 62 feeds from the float chamber i1. a

(b) A non-air vented nozzle which normalis in free communication with the float chamber I! through the passage 61 (Fig. 4).

This combination of a plain nozzle construction constant mixture departurest from a constant mixture ratio so that the economy at all speeds can be positively and easily controlled.

Briefly the nozzle 60 tends to become richer at high air flows; the air vented well ll tends to be come leaner, hence either tendency can be arranged to overcome the other as desired. The low speed fuel is drawn from the lower portions of the air Venturl well It thru the passage ii-ll which discharges into the chamber H where a little air is mixed with it and then the ail-and fuel discharges thru it; as the throttle i2 opens the nozzle it also" discharges. 'I'hen as the depression in it increases the fuel from 82 flows bothout of l9l9' -and out of IO. Finallyat extremely high speeds the depression in the throat of i4 is such that all the fuel that enters It at '2 flows up out of i8 and none flows thru II-l3 to I4, but normally this does not talre place.

In the Figures 1 to 11, Ills the air entrance leaning to a Venturi throat Ii in whlchis located which gives a substantially (Fig. 3). A small venturi "discharges at H on the atmospheric side of the-throttletf. 1 I In Figure 6, I8 is an air vented fuel well having an outlet l8 discharging into ll-and a restricted fuel entrance or located in the bottom or the float chamber ii with the accelerating pump shown in Fig; 4 through the fuel passage 61 (see Figs. 1, 4, '6 and 10) is mounted inside the perforated tube 65 but is separatetherefroln.

The perforated sleeve .65 divides the air vented well i8 into'two'parts; an inner one which discharges through II and an outer one which is connected with the atmosphere at 64 in its upper end. At its lower end a low speed fuel outlet 88 is provided, which is connectedwith the fuel pasgggeg l9, ii, 12, it and it to the low speed fuel outlet |9--i8' as follows:

Fuel for the low speednozzle ls -lr (shown in Fig. 5) is drawn up the Passages 69 9 the y 2,080,009 Fig. 15 showsthemethodofmeasuringthedenozzle with on all chamber ll through the by the throttle spond to Patent no.

and connected with ll through til.

"denly opened then P ston 92.

it enters the mixture chamber ll through the double low speed fuel outlets .iO-'ll' travelling through the passage 1! and II to the small chamber H. The double outlet li-i! .is located adjacent to and on the engine side of the throttle I! so that as the throttle opens the flow through I9 increases and its flow is added to that flowing thru the upper oriflce l9.

The power Jet (see Figs. 1 and 6) obtains its supply of fuel direct from the float chamber ll through the passage 18 and the restricted opening I! (see Figs. 7, 8 and 9) in which Fig. 7 shows the throttle ti open. Fig. 58 shows the throttle closed and Fig. 9 shows the throttle wide open. The nozzle is connected through a passage 6| with a small chamber 18 (see Figs. l, 6,-'!, 8 and 9). Into an air vented well." a tube 84 dips which discharges into the small chamber it which communicates through the restricted passage ill with the power mixing chamber. (which is the throat ii) on the atmospheric side of the throttle i2.

In the throttle position shown in Fig. 8, the maximum economy is obtained, a passage 1! bepassage Il-QHI. III is a passage drilled in the throttleshaft It which acts as a valve controlled by the throttle II. When the throttle is closed (Fig. 8) the throttle valve 8 puts the air entrance II in communication wziththe chamber 18 through the inclined passage 8 In the position shown in Fig. '7, the flowfrom 7 II to I! is obstructed by the partial closing of 80 and air flows down from II to the inclined passage 83 which leads into the upper portion of the well 11. This gives an increased fuel flow- In the Fig. 9 the passage ll Acceleration (Fig. 1). This pump is operated shaft II to which ball end 90 is beyond that of the clearance provided in the cupl so that if the throttle is sudwill strike the back of the 10 means The starting means comprise a starting fuel nomle 8! fed from the float chamber I! (see Fig. 3) and lschargin lnto the well It, vented by means of the tube 34 which has a Small hole is completely blocked at its upper end to break the siphoning action which would otherwise take place. This tube communicates through 99 with 99 which is in free communication with the air entrance III.

A passage 31 conveys fuel and air to the vertical passage 98 down which it flows to connect thru 99 into the chamber 28 whence the fuel is discharged thru II into the mixture outlet 20. A starting valve ll'lwith a stop ll which engages with the carburetor casting 49 controls both the mixture outlet from 28 into the priming passage II and the entrance of the fuel from the passage 99 into the air chamber 29. A rod 54 mounted in II engages with a disc valve 52 with openings 52. A valve 26 is mounted on 53 so as to close the openings 52 by its valve seat 21,

passage 22 which is controlled by the adjustable screw 23 (Fig. 11).

This passage supplies air to mingle with the fuel discharged at the lip of throttle l2 out of the opening l9 and thus makes an explosive mixture in 30 when the throttle valve I2 is completely closed. The screw 28 (Fig. 11) thus corresponds to the throttle stop ordinarily used with carburetors, the adjustment of which determines the idling speed.

This novel low speed and starting control is the subject of another patent application.

. Operation The carburetor is started with the throttle completely closed. A very rich mixture is thus drawn from the float chamber i I out of the well 33 (Fig. 3) down the passage 31-99 together with the air drawn through 34. This fuel and air discharges through 39 and flows through 3| into the mixture outlet 30. The moment the engine begins to fire the vacuum in the inlet manifold acting through 30 is communicated thru the passage 22 to the passage 24 and the piston rises under the action of atmospheric air acting on the outside of the valve 26 thereby uncovering the openings 52 in the plate 53 and thereby permitting air to flow into the chamber 29. Thermostatic means not shown may be provided for moving the piston 40 which first raises the valve 98 giving a fast idle immediately and gradually cuts off the priming fuel of 39 and the outlet passage II. This is the subject of co- ,pending appl cation Serial #616,278 and U. S.

Patent 1,998,581.

The low speed fuel supply of the engine is then obtained through the double fuel outlets l9|9'.

This fuel flows from the float chamber l'l (Figs. 5 and 6) thru the restriction 62 up the passage 69 across the passage 68, up the passage 69, thru the restriction H, into the chamber Iii, where air is admitted past the regulating idle screw 99. The rich mixture iiows across '12 and 13 into the chamber II out of which it flows through l9 into the venturi ll adjacent to and just in advance of the upstream lip of the throttle i2.

The idling adjustment is'made by regulating the fuel supply by the screw 23 (Fig. 11) and the air supplyby the screw 99 (Fig. 5). 99 is screwed in to give a richer mixture and 23 is screwed out to give a higher speed.

If the throttle is opened, the nozzles l9-l9' increase the fuel flow in a well known manner. Meanwhile the fuel level in i9 is thereby slightly lowered to prevent the premature discharge of time fuel flows from the pump chamber (shown thru 61 and at the same time closes the check valve 95. Meanwhile the throttle shaft l2 has been rotating so as to move the passage out of line with the passage ill (see Fig. 8) and to provide the extrav fuel required when running with a wide open throttle.

In Fig. 7 the passage is sufllcie ntly obstructedv so that air flows from 19 down 83 and displaces I the fuel in' the well 11. This fuel-being discharged thru the opening 6i which discharges fuel into the throat of the venturi ll thru the nozzle 95.. This hole is drilled in the shaft l3 at such an angle that the fuel flow thru Bl does not become appreciable until the throttle is opened beyond the normal economical running condition of the throttle. 'In other words,. the throttle is opened for power when economy is no longer of primary importance. The fuel nozzle 95 is commonly referred to as a power jet- Fuel for the well 19 is obtained directly from the float chamber I 1 thru the restriction 15. When the throttle is wide open the passage 80 completely obstructs the passage II. t

It will be noted that the mixture is formed by fuel issuing into N on both sides of the throttle l2 and that the distance fromv I3 to the flange is much greater than is commercially possible when the throttle I2 is located in the mixture outlet 30 and instead of in the throat II of the venturi Ill-40. This distance is a vital factor in facilitating the desired uniform distribution of the fuel on the air stream which determines the ultimate distribution of the mixture to the engine cylinders.

Figures 13, 14 and 15 illustrate diagrammatically the difference between the applicants construction, Figure 14, and the prior art (illustrated in Figure 15). Both the curves. in Figure 13 represent the vacuum obtained at the throat of the smaller of the two venturis,. I4 and l4.- The upper curve carries also the corresponding throttle portion required at normal operation running on a level boulevard to create the manifold vacuum against which the depressi0n in the throat of the smaller venturis is plotted. In both cases the idling vacuum at 23". throttle is 18 of mercury. At 23 throttle position, that is, when idling. there is no measurable depression in the throat of either of the two smaller venturis I9 and H. Now corresponds to wide-open throttle, therefore, 90' minus 23 equals 67 constitutes the movement to wideopen throttle position. The curves are plotted justshort of opening corresponding to 74.7 throttle position. At this position the manifold vacuum has fallen to just over '2" of mercury when running on a level boulevard and the depression in the small venturi ll of Figure '14 has now risen to 47" of water, but the curve is flattening out and has practically ceased to rise (upper curve).

In the case of the orthodox carburetor shown in Figure 15, the depression in H has only risen to 33" of water (lower curve), but this depression is rapidly rising so that at wide-open throttle 90,the two curves will approach each other very closely or most probably actually meet. Thisis because the net throat areas of the two carburetors were selected so as to be the same, hence the velocities of air at wide-open throttle are substantially the same for substantially the same cubic feet per minute flow. The reason for the marked difference between the two curves at part throttle. is that by reason of the location of the throttle in the embodiment shown 'in Figure 14 in the throat ll of the main venturi, it follows that when partly closed, most of the air is, guided by the throttle so as to flow through the portion of the passage on the right side of the throttle I2 and hence the velocity of the air on that side increases and the pressure in H drops due to the diversion of the air stream over the mouth of the smaller venturi.

What I claim is:

1. In a carburetor the combination of a mixture chamber of Venturi form having a restricted throat, a throttle located in the throat, a smaller Venturi having its axis inclined to the axis of 'the main Venturi and discharging into the throat of the main venturi against said throttle valve and on the atmospheric side thereof whereby the outlet from the smaller Venturi is restricted when the throttle is in its closed position, a constant levellfuel ,supply chamber, an air vented fuel well fed therefrom, an air and fuel outlet from said well discharging into the throat of said smaller venturi.

2. In' a carburetor for an internal combustion engine, a mixing chamber of the Venturi form having a restricted throat, a butterfly throttle valve therein, a fuel supply chamber, a fuel outlet therefrom, an air vented reservoir into which said outlet discharges, an outlet from the upper part of said reservoir discharging into said throat on the atmospheric side of and against said throttle, said throttle being located so as to divert when partly closed the main air flow past said outlet, a low speed fuel outlet so located in said Venturi as to discharge against the opposite side of said throttle and so as to be progressively subjected to the engine suction as the throttle is moved from the closed position, a passage connecting said low speed fuel outlet with an outlet from the lower portion of said reservoir.

3. In a carburetor for an internal combustion engine, a mixing chamber having a restricted throat, a butterfly throttle valve located in the throat thereof, a fuel supply chamber, a fuel outlet therefrom discharging into an air vented reservoir associated therewith, an outlet from the upper part of said reservoir discharging into said mixing chamber against said throttle on the atmospheric side thereof, said throttle being located so as to divert when partly closed the main air flow past said outlet, a second outlet t erefrom discharging into said mixing chamr against said throttle on the engine side thereof and so located as to beprogressively subjected to the engine suction by the thro ttle as the throttle is moved from its closed position.

4. In a carburetor a Venturi tube having a restricted throat, a throttle valve therein, asmaller well fed therefrom, an air and fuel outlet from said well discharging into the throat of said smaller Venturi an unvented fuel nozzle also fed. from said fuel chamber and also discharging into the throat of said small venturi.

5. In a carburetor a main mixing tube of Ven-. turi form having a restricted throat, a. throttle valve therein, a smaller mixing tube having its axis inclined to the axis of the main mixing tube and discharging into the throat of said main mixing tube on the atmospheric side of and adiacent to said'throttle whereby the outlet from the smaller tube is restricted when the throttle is in its closed position, a constant level fuel supply chamber, an air vented fuel well fed therefrom, an air and fuel outlet from the upper part of said well discharging into said restricted throat on the atmospheric side of andterfly throttle mounted therein, means for discharging low speed fuel against the downstream half of said butterfly throttle on the engine side thereof and means adjacent to said throttle for discharging high speed fuel directly against the upstream half of said throttle and on the atmospheric side thereof, said throttle being so located that it diverts when partly closed the main air flow past said high speed fuel discharge means.

7. A carburetor for an internal combustion en- .gine having a mixture chamber of Venturi form,

a throat therefor having a butterfly throttle mounted therein, means for discharging low speed fuel against the downstream half of said butterfly throttle and on the engine side thereof and means adjacent to said throttle for discharging high speed fuel directly against the upstream half of said throttle and on the atmospheric side thereof, said throttle being so located that it diverts when partly closed the f main air flow past said high speed fuel discharge means.

8. A downdraft carburetor foran internal com- I bustion engine comprising a downdraft mixing chamber of Venturi form having a restricted throa a throttle ,valve therein, a mixture outlet leading therefrom, means adjacent to said throttle for discharslng'highspeedfuel into said mixing chamber adjacent to land above said throttle, means for dischargingilow speed fuel into said mixing chamber adjacent to and below; I

said throttle so as to. be progressively subjected to the suction of theengine asthe throttle is opened, said throttle being so located that it .di-

verts when partly closed the main air flow past said high speed fuel discharge means. g 9. A downdraft carburetor as set forth in claim 8, said throttle being a butterfly throttle.

10. A downdraft carburetor as set forth in claim 8, in which the means for discharging high speed fuel into said mixing chamber consists of a small Venturi discharging into said mixing chamber adjacent to and above said throttle and Patentllo. 2,080,569.

-11. A downdraft carburetor as in claim 8 in which the means for discharging high ,and low a small venturi discharging therein, a fuel nozzle discharging into the throat of the small ven turi and fed from the said supply chamber, a throttle located in the main mixing chamber on i the downstream side of the outlet from said small venturi and located so as to restrict when closed that portion of the mixing chamber into which the mouth of the small venturi discharges venturi discharges and to divert when partly open the main air flow past said mouth,

GEORGE M. HOLLEY.

CERTIFICATE OF CORRECTION. V

- speed fuels into said mixing chamber includes and to divert when partly open the main air flow 5 a constant level fuel supply chamber, an air past said mouth. vented fuel reservoir associated therewith, ahigh 15. In a carburetor having a constant level speed fuel outlet from the upper part of said fuel supply chamber, a main mixing chamber of reservoir and a low speed fuel outlet from the Venturl form, a small venturi discharging into 1 lower part thereof. the throat thereof, a fuel nozzle discharging into 10 12. A downdraft carburetor as 'set forth in the small venturi and fed from the said supply claim 8, in which the means for discharging high chamber, a throttle located in the throat of the speed fuel into said mixing chamber includes a main mixing chamber on the downstream side small venturi discharging into said mixing chamof the outlet from said small venturi and located her above said throttle, a constant level fuel supso as to restrict when closed the said throat into 15 ply chamber, an air vented fuel reservoir aswhich the mouth of the small venturi discharges sooiated-therewith, a high speed fuel outlet from and to divert when partly open the main air the upper part of said reservoir discharging into how past said mouth. the throat of said small venturi and an addi- 16. In a .carbu havinfl a o a t lev l tional high speed fuel nozzle independent of said fuel supply chamber, 'a main mixing chamber, a 20 air vented reservoir but fed from said constant small venturi discharging therein, a fuel nozzle level fuel supply chamber and also discharging discharging into the throat of the small venturi into the throat of said small venturi. and fed from the said supply chamber, a butter- 13. A downdraft carburetor as set forth in fly throttle located in the main mixing chamber claim 8, in which the means for discharging high on the downstream side of the outletfrom said 25 and low speed fuel into said mixing chamber small venturi and located so as to restrict when includes a small venturi discharging into said closed that portion of the mixing chamber into mixing chamber above said throttle, a constant which the mouth of the small venturi discharges level fuel supply chamber, an air vented fuel .and to divert when partly open the main air reservoir associated therewith, a high speed fuel flow past said mouth. 30 outlet from the upper part of said reservoir dis- In a carburetor hav ng 8- c nst nt evel charging into the throat of said small venturi fuel supply chamber, a main mixing chamber of and a low speed fuel outlet leading from the venturi form, a small venturi discharging into lower portion of said reservoir to the low speed the throat thereof, a fuel nozzle discharging into fuel outlet in said mixing chamber and an adthe small venturi and fed from the said supply 35 ditional high speed fuel nozzle directly connected chamber, a butterfly v throttle located in the with said fuel chamber and discharging into the throat of the main mixing chamber on the throat of said small venturi. downstream side of the outlet from said small 14. In a carburetor, having a constant level venturi and located so'as to restrict when closed 40 fuel supply chamber, a main mixing chamber, the said throat into which the mouth of the small 0 GEORGE: M. HOLLEY.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5 first column, line 36, for the word "fuel" read constant level fuel sup- I ply; and that the said Letters Patent should be read: with this correction Sitter em that the same may conform to the record of the case in the Patent ice. I Signed and sealed this 24th day of August, A. D. 1957.

Leslie'Frazer (Seal) Acting Commissioner: of Patents.

chamber adjacent to and above said throttle and Patentllo. 2,080,569.

-11. A downdraft carburetor as in claim 8 in which the means for discharging high ,and low a small venturi discharging therein, a fuel nozzle discharging into the throat of the small ven turi and fed from the said supply chamber, a throttle located in the main mixing chamber on i the downstream side of the outlet from said small venturi and located so as to restrict when closed that portion of the mixing chamber into which the mouth of the small venturi discharges venturi discharges and to divert when partly open the main air flow past said mouth,

GEORGE M. HOLLEY.

CERTIFICATE OF CORRECTION. V

- speed fuels into said mixing chamber includes and to divert when partly open the main air flow 5 a constant level fuel supply chamber, an air past said mouth. vented fuel reservoir associated therewith, ahigh 15. In a carburetor having a constant level speed fuel outlet from the upper part of said fuel supply chamber, a main mixing chamber of reservoir and a low speed fuel outlet from the Venturl form, a small venturi discharging into 1 lower part thereof. the throat thereof, a fuel nozzle discharging into 10 12. A downdraft carburetor as 'set forth in the small venturi and fed from the said supply claim 8, in which the means for discharging high chamber, a throttle located in the throat of the speed fuel into said mixing chamber includes a main mixing chamber on the downstream side small venturi discharging into said mixing chamof the outlet from said small venturi and located her above said throttle, a constant level fuel supso as to restrict when closed the said throat into 15 ply chamber, an air vented fuel reservoir aswhich the mouth of the small venturi discharges sooiated-therewith, a high speed fuel outlet from and to divert when partly open the main air the upper part of said reservoir discharging into how past said mouth. the throat of said small venturi and an addi- 16. In a .carbu havinfl a o a t lev l tional high speed fuel nozzle independent of said fuel supply chamber, 'a main mixing chamber, a 20 air vented reservoir but fed from said constant small venturi discharging therein, a fuel nozzle level fuel supply chamber and also discharging discharging into the throat of the small venturi into the throat of said small venturi. and fed from the said supply chamber, a butter- 13. A downdraft carburetor as set forth in fly throttle located in the main mixing chamber claim 8, in which the means for discharging high on the downstream side of the outletfrom said 25 and low speed fuel into said mixing chamber small venturi and located so as to restrict when includes a small venturi discharging into said closed that portion of the mixing chamber into mixing chamber above said throttle, a constant which the mouth of the small venturi discharges level fuel supply chamber, an air vented fuel .and to divert when partly open the main air reservoir associated therewith, a high speed fuel flow past said mouth. 30 outlet from the upper part of said reservoir dis- In a carburetor hav ng 8- c nst nt evel charging into the throat of said small venturi fuel supply chamber, a main mixing chamber of and a low speed fuel outlet leading from the venturi form, a small venturi discharging into lower portion of said reservoir to the low speed the throat thereof, a fuel nozzle discharging into fuel outlet in said mixing chamber and an adthe small venturi and fed from the said supply 35 ditional high speed fuel nozzle directly connected chamber, a butterfly v throttle located in the with said fuel chamber and discharging into the throat of the main mixing chamber on the throat of said small venturi. downstream side of the outlet from said small 14. In a carburetor, having a constant level venturi and located so'as to restrict when closed 40 fuel supply chamber, a main mixing chamber, the said throat into which the mouth of the small 0 GEORGE: M. HOLLEY.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5 first column, line 36, for the word "fuel" read constant level fuel sup- I ply; and that the said Letters Patent should be read: with this correction Sitter em that the same may conform to the record of the case in the Patent ice. I Signed and sealed this 24th day of August, A. D. 1957.

Leslie'Frazer (Seal) Acting Commissioner: of Patents. 

